Nondiscoloring stabilized vinyl chloride resin compositions



Jan. 8, 1952 S. M. KINZINGER NONDISCOLORING STABILIZED VINYL.A

CHLORIDE RESIN COMPOSITIONS Filed Feb. 18, 1950 3 n ven tor 5756/12/50 M, /f//vz//vefa 4 Cttornegs Patented Jan. 8, 1952 l,UNITED STATES PATENT 2,581,908 OFFICE NoNDIscoLoRING s'rAmLlzEn VINYL] cnLoaInn RESIN coMrosrrroNs` Siegfried M. Kinzinger, Pottstown, Pa., assignor to The Firestone Tire da Rubber Company, Akron, Ohio, acorporation o'f Ohio Application February 18, 1950, Serial No. 155,697

vent the aging of the finished article. These stabilizing compounds have the disadvantage that they cause discoloration of the finshed article when exposed to atmospheres containing hydrogen sulfide in even minute quantities. Such exposure occurs rather frequently; for instance, if a film is made up into a refrigeration dish cover or an apron having an elastic drawstring, the vulcanized rubber in the elastic drawstring gives off sufficient quantities of hydrogen sulfide to cause discoloration; similarly, if an artificial leather is employed in connection with a foamed rubber cushion, the hydrogen sulfide given off by the foamed rubber speedily causes discoloration; likewise if articles of this nature are packed in cardboard shipping boxes containing sulfur compounds derived from the pulping process. discoloration is apt to occur.

Accordingly, it is an object of this invention' to provide vinyl chloride resin compositions which are not deteriorated by the heat and friction of fabrication, or by subsequent action of light and air, and which also are not discolored by exposure to hydrogen sulfide.

Another object is to provide vinyl chloride resin compositions containing organic cadmium compounds which will not be discolored by the action of hydrogen sulfide.

A further object is to secure the above objects in compositions which are inexpensive, are readily processed by existing equipment and procedures, and have mechanical properties unchanged from those of the conventional vinyl chloride resin compositions.

SYNOPSIS OF THE INVENTION V The above and other objects are secured, in acmeans of conventional techniques and apparatusinto products having the same physical prop- 7 calins rc1. 26o-45.2)

erties and characteristics as corresponding products heretofore manufactured from vinyl resins. Inasmuch as the problem of discoloration by hydrogen sulfide is most severe in the case of sheeted products such as films, artificial leather, etc., the invention is of particular application to vinyl chloride resins fabricated into these articles.

The accompanying drawing illustrates a conventional refrigerator dish cover made from the composition of this invention. Such a refrigerator dish cover will not show discoloration due to hydrogen sulfide gas, as explained hereinbelow in Example I.

THE AMINOPLAST CONDENSATE The aminoplast condensates employed in this invention may be any of the well-known condensates of-urea, or of melamine, with formaldehyde, varying in degree of condensation all the way from the simple preliminary adducts such as methylolurea or dimethylol urea, or the simple mono, di and tri methylol adducts of melamine, down to, but not including, the final thermoset. infusible and insoluble cured condensates. In the terminology of thermosetting resins, the aminoplast condensates employed in this invention range through the A and B stages of condensation, but do not include the C" stage condensates, as these last are unworkable solids which could not be blended with the vinyl chloride resin compositions. lIn general, these condensates will contain from about 1 to about 3 moles of formaldehyde for each mole of urea or of melamine entering into the synthesis thereof. The condensates employed in this invention may also have condensed therein minor proportions (say up to 0.1l mole per mole of urea or melamine) of aliphatic alcohols. A more detailed description of the processes employed in the condensation of formaldehyde with urea and with melamine will be found in Nauth, "The Chemistry and Technology of Plastics (Reinhold), Chapter 3, pp. -91, and Wakeman, "The Chemistry of Commercial Plastics (Reinhold), Chapter 7,

pp. 171-196 (on urea condensates) and Chapter 8, pp. 197-207 (on melamine condensates) As to the amount of the aminoplast condensate to be employed, as little as 0.5%, based on the weight of vinyl chloride resin in the composition, will materially inhibit any discoloration due to the interaction of hydrogen sulfide and any cadmium stabilizers which may be present. The maximum amountwhic vis possible to employ is the maximum hich is compatible with the vinyl chlo .iuefresinz in generan, vinyl chloride resin compositions will tolerate at least as high as 10% of aminoplast condensate, based on the weight of vinyl chloride resin in the composition. It will be preferred, in most cases, to employ from 1% to 3%, based on the weight of THE CADMIUM-CONTAINING ORGANIC COMPOUND STABILIZERS It has been found that cadmium compounds containing organic groups 'capable of solubilizing the compounds in the vinyl chloride resins very effectively stabilize these resins against deterioration by heat and friction during fabrication and also protect the articles finally produced from the resins against aging due to light and atmospheric action. 'A particularly advantageous subdivision of these compounds are the cadmium alkyl mercaptides, the molecules of vwhich contain two alkyl groups each containing from to 26 carbon atoms, which alkyl groups are linked to the cadmium atom through divalent sulfur atoms. Cadmium mercaptides of this type are readily compatible with vinyl resins and enable them to be. worked (milled. calendered, etc.) at unconventional and extremely high temperatures for extremely long times. For instance, they permit working at 310-340 F. for periods of one-half to one hour; at 340- 380 F. for periods up to ten minutes; and .for periods of a minute or two at 400 C., as on a high speed calender. This permits of a much better fusion of the resin than is obtained in ordinary working, resulting in films and other products of outstanding clarity, homogeneity and strength, and in much higher permissible calendering speeds. Other cadmium compounds which may be used in the practice of this invention include the fatty acid' salts and soaps of cadmium such as cadmium diacetate, dibutyrate, dilaurate, dioleate, diabietate and the like. In general the fatty acid radical in these salts and soaps may contain from two to 26 carbon atoms. Likewise there may be employed mercaptides other than cadmium alkyl mercaptides, such as cadmium diphenyl mercaptide. Still further in addition there may be employed organometallic compounds involving cadmium such as dilauryl cadmium and the like. In general, these are compounds in which one or both of the valences of the cadmium atom are occupied by alkyl groups containing from one 'to 26 carbon atoms, any remaining valence being satisfied by a fatty acid radical containing from 1 to 26 carbon atoms or by a weak inorganic acid radical such as phosphate. borate, silicate, or the like. These cadmium stabilizers will be present in the compositions of this invention to the extent of from i 0.5 to 5.0%, based on the weight of vinyl chloride resin.

'IHE VINYL CHLORIDE RESINS The vinyl chloride resins are a well-known class of materials consisting of simple polymers of vinyl chloride, and copolymers of vinyl chloride in which the essential polyvinyl chloride polymer chains are interspersed at intervals with theresidues of other monoethylenically unsaturated compounds or conjugated diethylenically unsaturated compounds. In general, the essential character of the vinyl chloride polymer is unchanged, aside from a certain desirable increase in processibility and flexibility. by the inclusion therein of up to based on the total weight of the copolymer. of these extraneous-unsaturated compounds. vSuitable compounds for copolymerization with vinyl chloride include, for instance, vinyl esters on the order of `vinyl bromide, vinyl fluoride, vinyl acetate, vinyl chloroacetate, vinyl butyrate, other fatty acid vinyl esters, vinyl alkyl sulfonates and the like; vinyl ethers such as vinyl ethyl ether, vinyl isopropyl ether, vinyl chloroethyl ether and the like; cyclic unsaturated compounds such as styrene, the lmonoand polychloro-styrenes, coumarone.

indene, vinyl -naphthalenes, vinyl pyridines,

vinyl pyrroleand the like; acrylic acid and its derivatives such as ethyl acrylate, methyl methacrylate, ethyl methacrylate, ethyl chloroacrylate, acrylonitrile, methacrylonitrile, diethyl maleate, diethyl fumarate, and the like; vinylidene compounds on the order of -vinylidene chloride, vinylidene bromide, vinylidene fluorochloride, and the like; unsaturated hydrocarbons such as ethylene, propylene, is'obutene and the like; allyl compounds such as allyl acetate, allyl chloride, allyl ethyl ether and the like; and conjugated and cross-conjugated ethylenically unsaturated compounds such as butadiene, isoprene, chloroprene, 2,3-dimethylbutadiene-1,3, piperylene, divinyl ketone and the like. For a fairly complete list of materials known to polymerize with vinyl chloride, reference may be had to Krczil, Kurzes Handbuch der Polymerisations-Technik-II Mehrstoff Pol-- ymerization, Edward Bros. Inc., 1945, pp. '735- 747, the items under Vinyl chlorid. As a rough rule, the criterion of a practical comonomer for use with vinyl chloride to produce copolymers containing from 20% or more of vinyl chloride is that, on a mole percentage basis, an initial charge of 96% vinyl chloride, balance comonomer, shall yield an initial copolymer containing (a) at least vinyl chloride, and (b) not more than 99% vinyl chloride. On this basis, satisfactory comonomers for use with vinyl chloride will be those having Q2 and e2 values, as described in J. Polymer Science 2:101,

correlated as follows, assuming for vinyl chloride Qvinyl chloride-:.03 and e vinyl chlorlde=3 Instead of the singleunsaturated comonomers of the types above indicated, mixtures of such comonomers may enter into the copolymers, it'

being understoodthat the total quantity thereof shall be small enough (i. e., not over 20%, based on the weight of copolymer) that the essential character of the polyvinyl chloride chain is retained.

PROPERTIES AND USES OF THE COMPOSI- I'IONS OF 'I'H'IS INVENTION Hydrogen sulfide gas concentrations sufilcient common type of exposure, and one which isalmost certain to cause discoloration, occurs Example I Parts Geon 101" (a polyvinyl chloride manu- Example Ils-Rubber band contact test A series of films was niia'de up using the same basic formulation (resin, plastlciser. calcium stearate, calcium mercaptide) as in Example I, with various proportions of various ureaand melamine-formaldehyde condensates asset out hereinafter in Table II. In each case, the ingredients, together with the selected condensate, were compounded in a Banbury mill at 320 F.,

factured by the B. F. Goodrich Co.) 32 and then calendered out at the same temperature Geon 202" (a copolymer of approximately 20 into a film .004 inch thick. The resultant films 94% vinyl chloride, 6% vinylidelle 0h10- were then wrapped upon cylindrical mandrels, gd? manufactured by the B- F- Goodrich 16 and elastic rubber bands were wrapped there- -jaround. The assemblies were placed in an oven Plasticiser SC (a Hester 0f tfieihylene maintained at 40 c. and 95% relative humidity.

glycol with mixed saturated aliphatic 2:, s t f th h with T b1 n h t monobasic acids containing from 6 to 8 e or ere m a' e are t e ypes carbon atoms) 15 and amounts of ureaand melamine-formalde- Calcium stearate 0.3 hyde condensates employed in the several mms' Cadmium dilauryl mercaptide 0 75 together with the extent of discoloration of the Ureaforma1dehyde or melamine formalde.. portions Of the nlms Contacting the rubber bndS hyde condensate (per Table I) Per Table I at the intervals of time noted.

'TABLE ll Amount Discoloration After Exposure For- Stubilizcr Used.

par i 1 day 2 days 4 days l week None 0 yellow.... deep yellow... deep ye1low deep yellow, Beetle 210-8 (Manufactured hy the Amorican 1.3 none none none none.

Cyanamide and Chemical Corp.; an alkylated urea-formaldehyde B-stage condensate). c Dmethylol urea faint yeilow ramt yellow, Dimethylol urea nono nqne, Beetle 7278 (Manufactured by the American .....do.. faint yellow.

Cyauamidc and Chemical Corp.; an aikyy lated urea-formaldehyde condensate (i3-stage condensate. i Melmac 7273 (Manufactured by the American l. 3 .do'. do do nono.

Cyanamide and Chemical Co a mclamine-iormaldehyde B-stage con cnsate). B-stage urea-formaldehyde condensate 1.3 .do do faint ycllow mint yellow A series of compositions was made up in accordance with the above recipe, using various formaldehyde-urea and -melamine condensates in the several compositions in respective amounts as indicated in Table I. In each case the materials were milled together on a roll mill at 300 F. until a homogenous blend was obtained, after which the blend was transferred to a The foregoing accelerated test was found to correlate well with actual service, and refrigerator bowl covers fabricated from those of the above films containing condensates with elastic rubber drawstrings withstood long periods of service without discoloration.

Example IIL-Artificial leather Parts calender maintained at 320 and sheeted out vinyl chloride vnylidene chloride copoly thereon to form lms Inch thick. The mer (uGeon n manufactured b the presence of the cadmium mercaptide stabilizer B F Goodrich C'o a co ol mer ofygiq permitted the working at unconventionally high vinyl chlorides gq vil; dene chlo temperatures as described above, which resulted ride) o y 100 in exceptionally thorough fusing of the resin and 'f consequent improved clarity and tensile strength o5 Ilozlilthyl hexyl) phthalate of the product lm. ""."T

A sample'of each film was exposed for l hour sgsg pigment in an atmosphere saturated with water vapor Cadmium dnaurylgl'eR-E 2 and containing 026% by volume of hydrogen Melmac '7273 (a melamiide-forin-ald-eli-de sulfide gas. Each of the samples containing a 7o y condensation product remained perfectly clear at the end of the test. lA film prepared by the same procedure from the ingredients of the above schedule, but omitting the condensation product, was badly yellowed at the end of the test.

condensate manufactured by the American Cyanamide and Chemical Corp.) 0or2 Two artificial leathers were made up in accordance with the foregoing schedule, one with and one without the melamine-formaldehyde ,the artificial leather prepared as above described and containing the condensate withstood extended periods of service without discoloration of the leather.

From the foregoing general discussion and detailed speciilc examples, it will be evident d that this invention makes possible the use, in

vinyl -chloride resin lms and articial leathers, of the highly eifective cadmium stabilizers, without the sensitivity to discoloration by hydrogen sulfide usually attendant upon the use of these stabilizers. The ureaand melamine-formaldehyde condensates employed in the practice f this invention are readily compatible with the vinyl chloride resin compounds and, when employed in the relatively smallamounts required for the effective practice of this invention, do not measurably aiect the general chemical or physical properties of the compositions,

What is claimed is:

1. A composition stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising (l) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof withother unsaturated compounds copolymerizable therewith and containing at least 80% of vinyl chloride copolymerized therein (2) a cadmium mercaptide and (3) a condensate selected from the group consisting of urea-formaldehyde and melamineformaldehyde condensates.

2. A composition stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising 1) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof with other unsaturated compounds copolymerizable therewith and containing at least 80% of vinyl chloride copolymerized therein (2) an organic cadmium compound heat and light stabilizer and (3) a urea-formaldehyde condensate.

3. A composition stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising (1) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof with other unsaturated compounds copolymerizable therewith and containing at least of vinyl chloride copolymerized therein (2) a cadmium mercaptide and (3) a urea-formaldehyde condensate.

4. A composition stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising (1) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof with other unsaturated compounds copolymerizable therewith and containing at least 80% of vinyl chloride copolymerized therewith (2) an organic cadmium compound heat and light stabilizer and (3) a melamine-formaldehyde condensate.

5. A composition stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising (l) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof and containing at least 80% of vinyl chloride copolymerizable therein (2) a cadmium mercaptide and (3) a melamine-formaldehyde condensate.

v6. A thin, flexible, self-supporting film stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising (l) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof with other unsaturated compounds copolymerizable therewith and containing at least 80% of vinyl chloride copolymerized therein (2) a cadmium mercaptide and (3) a urea-formaldehyde condensate.

7. Av thin, flexible, self-supporting film stable to heat and light and resistant to discoloration by contact with hydrogen sulfide comprising (l) a resin selected from the group consisting of polymers of vinyl chloride and copolymers thereof with other unsaturated compounds copolymerizable therewith and containing at least 80% of vinyl chloride copolymerized therein (2) a cadmium mercaptide and (3) a melamine-formaldehyde condensate.

SIEGFRIED M. KINZINGER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,310,449 Lightbown et al. Feb. 9, 1943 2,364,172 Stauifer Dec. 5, 1944 

1. A COMPOSITION STABLE TO HEAT AND LIGHT AND RESISTANT TO DISCOLORATION BY CONTACT WITH HYDROGEN SULFIDE COMPRISING (1) A RESIN SELECTED FROM THE GROUP CONSISTING OF POLYMERS OF VINYL CHLORIDE AND COPOLYMERS THEREOF WITH OTHER UNSATURATED COMPOUNDS COPOLYMERIZABLE THEREWITH AND CONTAINING AT LEAST 80% OF VINYL CHLORIDE COPOLYMERIZED THEREIN (2) A CADMIUM MERCAPTIDE AND (3) A CONDENSATE SELECTED FROM THE GROUP CONSISTING OF UREA-FORMALDEHYDE AND MELAMINEFORMALDEHYDE CONDENSATES. 